workbench/libs/jpeg/jdinput.c

   1 /*
   2  * jdinput.c
   3  *
   4  * Copyright (C) 1991-1997, Thomas G. Lane.
   5  * Modified 2002-2013 by Guido Vollbeding.
   6  * This file is part of the Independent JPEG Group's software.
   7  * For conditions of distribution and use, see the accompanying README file.
   8  *
   9  * This file contains input control logic for the JPEG decompressor.
  10  * These routines are concerned with controlling the decompressor's input
  11  * processing (marker reading and coefficient decoding).  The actual input
  12  * reading is done in jdmarker.c, jdhuff.c, and jdarith.c.
  13  */
  14
  15 #define JPEG_INTERNALS
  16 #include "jinclude.h"
  17 #include "jpeglib.h"
  18
  19
  20 /* Private state */
  21
  22 typedef struct {
  23   struct jpeg_input_controller pub; /* public fields */
  24
  25   int inheaders;                /* Nonzero until first SOS is reached */
  26 } my_input_controller;
  27
  28 typedef my_input_controller * my_inputctl_ptr;
  29
  30
  31 /* Forward declarations */
  32 METHODDEF(int) consume_markers JPP((j_decompress_ptr cinfo));
  33
  34
  35 /*
  36  * Routines to calculate various quantities related to the size of the image.
  37  */
  38
  39
  40 /*
  41  * Compute output image dimensions and related values.
  42  * NOTE: this is exported for possible use by application.
  43  * Hence it mustn't do anything that can't be done twice.
  44  */
  45
  46 GLOBAL(void)
  47 jpeg_core_output_dimensions (j_decompress_ptr cinfo)
  48 /* Do computations that are needed before master selection phase.
  49  * This function is used for transcoding and full decompression.
  50  */
  51 {
  52 #ifdef IDCT_SCALING_SUPPORTED
  53   int ci;
  54   jpeg_component_info *compptr;
  55
  56   /* Compute actual output image dimensions and DCT scaling choices. */
  57   if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom) {
  58     /* Provide 1/block_size scaling */
  59     cinfo->output_width = (JDIMENSION)
  60       jdiv_round_up((long) cinfo->image_width, (long) cinfo->block_size);
  61     cinfo->output_height = (JDIMENSION)
  62       jdiv_round_up((long) cinfo->image_height, (long) cinfo->block_size);
  63     cinfo->min_DCT_h_scaled_size = 1;
  64     cinfo->min_DCT_v_scaled_size = 1;
  65   } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 2) {
  66     /* Provide 2/block_size scaling */
  67     cinfo->output_width = (JDIMENSION)
  68       jdiv_round_up((long) cinfo->image_width * 2L, (long) cinfo->block_size);
  69     cinfo->output_height = (JDIMENSION)
  70       jdiv_round_up((long) cinfo->image_height * 2L, (long) cinfo->block_size);
  71     cinfo->min_DCT_h_scaled_size = 2;
  72     cinfo->min_DCT_v_scaled_size = 2;
  73   } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 3) {
  74     /* Provide 3/block_size scaling */
  75     cinfo->output_width = (JDIMENSION)
  76       jdiv_round_up((long) cinfo->image_width * 3L, (long) cinfo->block_size);
  77     cinfo->output_height = (JDIMENSION)
  78       jdiv_round_up((long) cinfo->image_height * 3L, (long) cinfo->block_size);
  79     cinfo->min_DCT_h_scaled_size = 3;
  80     cinfo->min_DCT_v_scaled_size = 3;
  81   } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 4) {
  82     /* Provide 4/block_size scaling */
  83     cinfo->output_width = (JDIMENSION)
  84       jdiv_round_up((long) cinfo->image_width * 4L, (long) cinfo->block_size);
  85     cinfo->output_height = (JDIMENSION)
  86       jdiv_round_up((long) cinfo->image_height * 4L, (long) cinfo->block_size);
  87     cinfo->min_DCT_h_scaled_size = 4;
  88     cinfo->min_DCT_v_scaled_size = 4;
  89   } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 5) {
  90     /* Provide 5/block_size scaling */
  91     cinfo->output_width = (JDIMENSION)
  92       jdiv_round_up((long) cinfo->image_width * 5L, (long) cinfo->block_size);
  93     cinfo->output_height = (JDIMENSION)
  94       jdiv_round_up((long) cinfo->image_height * 5L, (long) cinfo->block_size);
  95     cinfo->min_DCT_h_scaled_size = 5;
  96     cinfo->min_DCT_v_scaled_size = 5;
  97   } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 6) {
  98     /* Provide 6/block_size scaling */
  99     cinfo->output_width = (JDIMENSION)
 100       jdiv_round_up((long) cinfo->image_width * 6L, (long) cinfo->block_size);
 101     cinfo->output_height = (JDIMENSION)
 102       jdiv_round_up((long) cinfo->image_height * 6L, (long) cinfo->block_size);
 103     cinfo->min_DCT_h_scaled_size = 6;
 104     cinfo->min_DCT_v_scaled_size = 6;
 105   } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 7) {
 106     /* Provide 7/block_size scaling */
 107     cinfo->output_width = (JDIMENSION)
 108       jdiv_round_up((long) cinfo->image_width * 7L, (long) cinfo->block_size);
 109     cinfo->output_height = (JDIMENSION)
 110       jdiv_round_up((long) cinfo->image_height * 7L, (long) cinfo->block_size);
 111     cinfo->min_DCT_h_scaled_size = 7;
 112     cinfo->min_DCT_v_scaled_size = 7;
 113   } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 8) {
 114     /* Provide 8/block_size scaling */
 115     cinfo->output_width = (JDIMENSION)
 116       jdiv_round_up((long) cinfo->image_width * 8L, (long) cinfo->block_size);
 117     cinfo->output_height = (JDIMENSION)
 118       jdiv_round_up((long) cinfo->image_height * 8L, (long) cinfo->block_size);
 119     cinfo->min_DCT_h_scaled_size = 8;
 120     cinfo->min_DCT_v_scaled_size = 8;
 121   } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 9) {
 122     /* Provide 9/block_size scaling */
 123     cinfo->output_width = (JDIMENSION)
 124       jdiv_round_up((long) cinfo->image_width * 9L, (long) cinfo->block_size);
 125     cinfo->output_height = (JDIMENSION)
 126       jdiv_round_up((long) cinfo->image_height * 9L, (long) cinfo->block_size);
 127     cinfo->min_DCT_h_scaled_size = 9;
 128     cinfo->min_DCT_v_scaled_size = 9;
 129   } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 10) {
 130     /* Provide 10/block_size scaling */
 131     cinfo->output_width = (JDIMENSION)
 132       jdiv_round_up((long) cinfo->image_width * 10L, (long) cinfo->block_size);
 133     cinfo->output_height = (JDIMENSION)
 134       jdiv_round_up((long) cinfo->image_height * 10L, (long) cinfo->block_size);
 135     cinfo->min_DCT_h_scaled_size = 10;
 136     cinfo->min_DCT_v_scaled_size = 10;
 137   } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 11) {
 138     /* Provide 11/block_size scaling */
 139     cinfo->output_width = (JDIMENSION)
 140       jdiv_round_up((long) cinfo->image_width * 11L, (long) cinfo->block_size);
 141     cinfo->output_height = (JDIMENSION)
 142       jdiv_round_up((long) cinfo->image_height * 11L, (long) cinfo->block_size);
 143     cinfo->min_DCT_h_scaled_size = 11;
 144     cinfo->min_DCT_v_scaled_size = 11;
 145   } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 12) {
 146     /* Provide 12/block_size scaling */
 147     cinfo->output_width = (JDIMENSION)
 148       jdiv_round_up((long) cinfo->image_width * 12L, (long) cinfo->block_size);
 149     cinfo->output_height = (JDIMENSION)
 150       jdiv_round_up((long) cinfo->image_height * 12L, (long) cinfo->block_size);
 151     cinfo->min_DCT_h_scaled_size = 12;
 152     cinfo->min_DCT_v_scaled_size = 12;
 153   } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 13) {
 154     /* Provide 13/block_size scaling */
 155     cinfo->output_width = (JDIMENSION)
 156       jdiv_round_up((long) cinfo->image_width * 13L, (long) cinfo->block_size);
 157     cinfo->output_height = (JDIMENSION)
 158       jdiv_round_up((long) cinfo->image_height * 13L, (long) cinfo->block_size);
 159     cinfo->min_DCT_h_scaled_size = 13;
 160     cinfo->min_DCT_v_scaled_size = 13;
 161   } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 14) {
 162     /* Provide 14/block_size scaling */
 163     cinfo->output_width = (JDIMENSION)
 164       jdiv_round_up((long) cinfo->image_width * 14L, (long) cinfo->block_size);
 165     cinfo->output_height = (JDIMENSION)
 166       jdiv_round_up((long) cinfo->image_height * 14L, (long) cinfo->block_size);
 167     cinfo->min_DCT_h_scaled_size = 14;
 168     cinfo->min_DCT_v_scaled_size = 14;
 169   } else if (cinfo->scale_num * cinfo->block_size <= cinfo->scale_denom * 15) {
 170     /* Provide 15/block_size scaling */
 171     cinfo->output_width = (JDIMENSION)
 172       jdiv_round_up((long) cinfo->image_width * 15L, (long) cinfo->block_size);
 173     cinfo->output_height = (JDIMENSION)
 174       jdiv_round_up((long) cinfo->image_height * 15L, (long) cinfo->block_size);
 175     cinfo->min_DCT_h_scaled_size = 15;
 176     cinfo->min_DCT_v_scaled_size = 15;
 177   } else {
 178     /* Provide 16/block_size scaling */
 179     cinfo->output_width = (JDIMENSION)
 180       jdiv_round_up((long) cinfo->image_width * 16L, (long) cinfo->block_size);
 181     cinfo->output_height = (JDIMENSION)
 182       jdiv_round_up((long) cinfo->image_height * 16L, (long) cinfo->block_size);
 183     cinfo->min_DCT_h_scaled_size = 16;
 184     cinfo->min_DCT_v_scaled_size = 16;
 185   }
 186
 187   /* Recompute dimensions of components */
 188   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
 189        ci++, compptr++) {
 190     compptr->DCT_h_scaled_size = cinfo->min_DCT_h_scaled_size;
 191     compptr->DCT_v_scaled_size = cinfo->min_DCT_v_scaled_size;
 192   }
 193
 194 #else /* !IDCT_SCALING_SUPPORTED */
 195
 196   /* Hardwire it to "no scaling" */
 197   cinfo->output_width = cinfo->image_width;
 198   cinfo->output_height = cinfo->image_height;
 199   /* initial_setup has already initialized DCT_scaled_size,
 200    * and has computed unscaled downsampled_width and downsampled_height.
 201    */
 202
 203 #endif /* IDCT_SCALING_SUPPORTED */
 204 }
 205
 206
 207 LOCAL(void)
 208 initial_setup (j_decompress_ptr cinfo)
 209 /* Called once, when first SOS marker is reached */
 210 {
 211   int ci;
 212   jpeg_component_info *compptr;
 213
 214   /* Make sure image isn't bigger than I can handle */
 215   if ((long) cinfo->image_height > (long) JPEG_MAX_DIMENSION ||
 216       (long) cinfo->image_width > (long) JPEG_MAX_DIMENSION)
 217     ERREXIT1(cinfo, JERR_IMAGE_TOO_BIG, (unsigned int) JPEG_MAX_DIMENSION);
 218
 219   /* Only 8 to 12 bits data precision are supported for DCT based JPEG */
 220   if (cinfo->data_precision < 8 || cinfo->data_precision > 12)
 221     ERREXIT1(cinfo, JERR_BAD_PRECISION, cinfo->data_precision);
 222
 223   /* Check that number of components won't exceed internal array sizes */
 224   if (cinfo->num_components > MAX_COMPONENTS)
 225     ERREXIT2(cinfo, JERR_COMPONENT_COUNT, cinfo->num_components,
 226              MAX_COMPONENTS);
 227
 228   /* Compute maximum sampling factors; check factor validity */
 229   cinfo->max_h_samp_factor = 1;
 230   cinfo->max_v_samp_factor = 1;
 231   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
 232        ci++, compptr++) {
 233     if (compptr->h_samp_factor<=0 || compptr->h_samp_factor>MAX_SAMP_FACTOR ||
 234         compptr->v_samp_factor<=0 || compptr->v_samp_factor>MAX_SAMP_FACTOR)
 235       ERREXIT(cinfo, JERR_BAD_SAMPLING);
 236     cinfo->max_h_samp_factor = MAX(cinfo->max_h_samp_factor,
 237                                    compptr->h_samp_factor);
 238     cinfo->max_v_samp_factor = MAX(cinfo->max_v_samp_factor,
 239                                    compptr->v_samp_factor);
 240   }
 241
 242   /* Derive block_size, natural_order, and lim_Se */
 243   if (cinfo->is_baseline || (cinfo->progressive_mode &&
 244       cinfo->comps_in_scan)) { /* no pseudo SOS marker */
 245     cinfo->block_size = DCTSIZE;
 246     cinfo->natural_order = jpeg_natural_order;
 247     cinfo->lim_Se = DCTSIZE2-1;
 248   } else
 249     switch (cinfo->Se) {
 250     case (1*1-1):
 251       cinfo->block_size = 1;
 252       cinfo->natural_order = jpeg_natural_order; /* not needed */
 253       cinfo->lim_Se = cinfo->Se;
 254       break;
 255     case (2*2-1):
 256       cinfo->block_size = 2;
 257       cinfo->natural_order = jpeg_natural_order2;
 258       cinfo->lim_Se = cinfo->Se;
 259       break;
 260     case (3*3-1):
 261       cinfo->block_size = 3;
 262       cinfo->natural_order = jpeg_natural_order3;
 263       cinfo->lim_Se = cinfo->Se;
 264       break;
 265     case (4*4-1):
 266       cinfo->block_size = 4;
 267       cinfo->natural_order = jpeg_natural_order4;
 268       cinfo->lim_Se = cinfo->Se;
 269       break;
 270     case (5*5-1):
 271       cinfo->block_size = 5;
 272       cinfo->natural_order = jpeg_natural_order5;
 273       cinfo->lim_Se = cinfo->Se;
 274       break;
 275     case (6*6-1):
 276       cinfo->block_size = 6;
 277       cinfo->natural_order = jpeg_natural_order6;
 278       cinfo->lim_Se = cinfo->Se;
 279       break;
 280     case (7*7-1):
 281       cinfo->block_size = 7;
 282       cinfo->natural_order = jpeg_natural_order7;
 283       cinfo->lim_Se = cinfo->Se;
 284       break;
 285     case (8*8-1):
 286       cinfo->block_size = 8;
 287       cinfo->natural_order = jpeg_natural_order;
 288       cinfo->lim_Se = DCTSIZE2-1;
 289       break;
 290     case (9*9-1):
 291       cinfo->block_size = 9;
 292       cinfo->natural_order = jpeg_natural_order;
 293       cinfo->lim_Se = DCTSIZE2-1;
 294       break;
 295     case (10*10-1):
 296       cinfo->block_size = 10;
 297       cinfo->natural_order = jpeg_natural_order;
 298       cinfo->lim_Se = DCTSIZE2-1;
 299       break;
 300     case (11*11-1):
 301       cinfo->block_size = 11;
 302       cinfo->natural_order = jpeg_natural_order;
 303       cinfo->lim_Se = DCTSIZE2-1;
 304       break;
 305     case (12*12-1):
 306       cinfo->block_size = 12;
 307       cinfo->natural_order = jpeg_natural_order;
 308       cinfo->lim_Se = DCTSIZE2-1;
 309       break;
 310     case (13*13-1):
 311       cinfo->block_size = 13;
 312       cinfo->natural_order = jpeg_natural_order;
 313       cinfo->lim_Se = DCTSIZE2-1;
 314       break;
 315     case (14*14-1):
 316       cinfo->block_size = 14;
 317       cinfo->natural_order = jpeg_natural_order;
 318       cinfo->lim_Se = DCTSIZE2-1;
 319       break;
 320     case (15*15-1):
 321       cinfo->block_size = 15;
 322       cinfo->natural_order = jpeg_natural_order;
 323       cinfo->lim_Se = DCTSIZE2-1;
 324       break;
 325     case (16*16-1):
 326       cinfo->block_size = 16;
 327       cinfo->natural_order = jpeg_natural_order;
 328       cinfo->lim_Se = DCTSIZE2-1;
 329       break;
 330     default:
 331       ERREXIT4(cinfo, JERR_BAD_PROGRESSION,
 332                cinfo->Ss, cinfo->Se, cinfo->Ah, cinfo->Al);
 333       break;
 334     }
 335
 336   /* We initialize DCT_scaled_size and min_DCT_scaled_size to block_size.
 337    * In the full decompressor,
 338    * this will be overridden by jpeg_calc_output_dimensions in jdmaster.c;
 339    * but in the transcoder,
 340    * jpeg_calc_output_dimensions is not used, so we must do it here.
 341    */
 342   cinfo->min_DCT_h_scaled_size = cinfo->block_size;
 343   cinfo->min_DCT_v_scaled_size = cinfo->block_size;
 344
 345   /* Compute dimensions of components */
 346   for (ci = 0, compptr = cinfo->comp_info; ci < cinfo->num_components;
 347        ci++, compptr++) {
 348     compptr->DCT_h_scaled_size = cinfo->block_size;
 349     compptr->DCT_v_scaled_size = cinfo->block_size;
 350     /* Size in DCT blocks */
 351     compptr->width_in_blocks = (JDIMENSION)
 352       jdiv_round_up((long) cinfo->image_width * (long) compptr->h_samp_factor,
 353                     (long) (cinfo->max_h_samp_factor * cinfo->block_size));
 354     compptr->height_in_blocks = (JDIMENSION)
 355       jdiv_round_up((long) cinfo->image_height * (long) compptr->v_samp_factor,
 356                     (long) (cinfo->max_v_samp_factor * cinfo->block_size));
 357     /* downsampled_width and downsampled_height will also be overridden by
 358      * jdmaster.c if we are doing full decompression.  The transcoder library
 359      * doesn't use these values, but the calling application might.
 360      */
 361     /* Size in samples */
 362     compptr->downsampled_width = (JDIMENSION)
 363       jdiv_round_up((long) cinfo->image_width * (long) compptr->h_samp_factor,
 364                     (long) cinfo->max_h_samp_factor);
 365     compptr->downsampled_height = (JDIMENSION)
 366       jdiv_round_up((long) cinfo->image_height * (long) compptr->v_samp_factor,
 367                     (long) cinfo->max_v_samp_factor);
 368     /* Mark component needed, until color conversion says otherwise */
 369     compptr->component_needed = TRUE;
 370     /* Mark no quantization table yet saved for component */
 371     compptr->quant_table = NULL;
 372   }
 373
 374   /* Compute number of fully interleaved MCU rows. */
 375   cinfo->total_iMCU_rows = (JDIMENSION)
 376     jdiv_round_up((long) cinfo->image_height,
 377                   (long) (cinfo->max_v_samp_factor * cinfo->block_size));
 378
 379   /* Decide whether file contains multiple scans */
 380   if (cinfo->comps_in_scan < cinfo->num_components || cinfo->progressive_mode)
 381     cinfo->inputctl->has_multiple_scans = TRUE;
 382   else
 383     cinfo->inputctl->has_multiple_scans = FALSE;
 384 }
 385
 386
 387 LOCAL(void)
 388 per_scan_setup (j_decompress_ptr cinfo)
 389 /* Do computations that are needed before processing a JPEG scan */
 390 /* cinfo->comps_in_scan and cinfo->cur_comp_info[] were set from SOS marker */
 391 {
 392   int ci, mcublks, tmp;
 393   jpeg_component_info *compptr;
 394
 395   if (cinfo->comps_in_scan == 1) {
 396
 397     /* Noninterleaved (single-component) scan */
 398     compptr = cinfo->cur_comp_info[0];
 399
 400     /* Overall image size in MCUs */
 401     cinfo->MCUs_per_row = compptr->width_in_blocks;
 402     cinfo->MCU_rows_in_scan = compptr->height_in_blocks;
 403
 404     /* For noninterleaved scan, always one block per MCU */
 405     compptr->MCU_width = 1;
 406     compptr->MCU_height = 1;
 407     compptr->MCU_blocks = 1;
 408     compptr->MCU_sample_width = compptr->DCT_h_scaled_size;
 409     compptr->last_col_width = 1;
 410     /* For noninterleaved scans, it is convenient to define last_row_height
 411      * as the number of block rows present in the last iMCU row.
 412      */
 413     tmp = (int) (compptr->height_in_blocks % compptr->v_samp_factor);
 414     if (tmp == 0) tmp = compptr->v_samp_factor;
 415     compptr->last_row_height = tmp;
 416
 417     /* Prepare array describing MCU composition */
 418     cinfo->blocks_in_MCU = 1;
 419     cinfo->MCU_membership[0] = 0;
 420
 421   } else {
 422
 423     /* Interleaved (multi-component) scan */
 424     if (cinfo->comps_in_scan <= 0 || cinfo->comps_in_scan > MAX_COMPS_IN_SCAN)
 425       ERREXIT2(cinfo, JERR_COMPONENT_COUNT, cinfo->comps_in_scan,
 426                MAX_COMPS_IN_SCAN);
 427
 428     /* Overall image size in MCUs */
 429     cinfo->MCUs_per_row = (JDIMENSION)
 430       jdiv_round_up((long) cinfo->image_width,
 431                     (long) (cinfo->max_h_samp_factor * cinfo->block_size));
 432     cinfo->MCU_rows_in_scan = (JDIMENSION)
 433       jdiv_round_up((long) cinfo->image_height,
 434                     (long) (cinfo->max_v_samp_factor * cinfo->block_size));
 435
 436     cinfo->blocks_in_MCU = 0;
 437
 438     for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
 439       compptr = cinfo->cur_comp_info[ci];
 440       /* Sampling factors give # of blocks of component in each MCU */
 441       compptr->MCU_width = compptr->h_samp_factor;
 442       compptr->MCU_height = compptr->v_samp_factor;
 443       compptr->MCU_blocks = compptr->MCU_width * compptr->MCU_height;
 444       compptr->MCU_sample_width = compptr->MCU_width * compptr->DCT_h_scaled_size;
 445       /* Figure number of non-dummy blocks in last MCU column & row */
 446       tmp = (int) (compptr->width_in_blocks % compptr->MCU_width);
 447       if (tmp == 0) tmp = compptr->MCU_width;
 448       compptr->last_col_width = tmp;
 449       tmp = (int) (compptr->height_in_blocks % compptr->MCU_height);
 450       if (tmp == 0) tmp = compptr->MCU_height;
 451       compptr->last_row_height = tmp;
 452       /* Prepare array describing MCU composition */
 453       mcublks = compptr->MCU_blocks;
 454       if (cinfo->blocks_in_MCU + mcublks > D_MAX_BLOCKS_IN_MCU)
 455         ERREXIT(cinfo, JERR_BAD_MCU_SIZE);
 456       while (mcublks-- > 0) {
 457         cinfo->MCU_membership[cinfo->blocks_in_MCU++] = ci;
 458       }
 459     }
 460
 461   }
 462 }
 463
 464
 465 /*
 466  * Save away a copy of the Q-table referenced by each component present
 467  * in the current scan, unless already saved during a prior scan.
 468  *
 469  * In a multiple-scan JPEG file, the encoder could assign different components
 470  * the same Q-table slot number, but change table definitions between scans
 471  * so that each component uses a different Q-table.  (The IJG encoder is not
 472  * currently capable of doing this, but other encoders might.)  Since we want
 473  * to be able to dequantize all the components at the end of the file, this
 474  * means that we have to save away the table actually used for each component.
 475  * We do this by copying the table at the start of the first scan containing
 476  * the component.
 477  * The JPEG spec prohibits the encoder from changing the contents of a Q-table
 478  * slot between scans of a component using that slot.  If the encoder does so
 479  * anyway, this decoder will simply use the Q-table values that were current
 480  * at the start of the first scan for the component.
 481  *
 482  * The decompressor output side looks only at the saved quant tables,
 483  * not at the current Q-table slots.
 484  */
 485
 486 LOCAL(void)
 487 latch_quant_tables (j_decompress_ptr cinfo)
 488 {
 489   int ci, qtblno;
 490   jpeg_component_info *compptr;
 491   JQUANT_TBL * qtbl;
 492
 493   for (ci = 0; ci < cinfo->comps_in_scan; ci++) {
 494     compptr = cinfo->cur_comp_info[ci];
 495     /* No work if we already saved Q-table for this component */
 496     if (compptr->quant_table != NULL)
 497       continue;
 498     /* Make sure specified quantization table is present */
 499     qtblno = compptr->quant_tbl_no;
 500     if (qtblno < 0 || qtblno >= NUM_QUANT_TBLS ||
 501         cinfo->quant_tbl_ptrs[qtblno] == NULL)
 502       ERREXIT1(cinfo, JERR_NO_QUANT_TABLE, qtblno);
 503     /* OK, save away the quantization table */
 504     qtbl = (JQUANT_TBL *)
 505       (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_IMAGE,
 506                                   SIZEOF(JQUANT_TBL));
 507     MEMCOPY(qtbl, cinfo->quant_tbl_ptrs[qtblno], SIZEOF(JQUANT_TBL));
 508     compptr->quant_table = qtbl;
 509   }
 510 }
 511
 512
 513 /*
 514  * Initialize the input modules to read a scan of compressed data.
 515  * The first call to this is done by jdmaster.c after initializing
 516  * the entire decompressor (during jpeg_start_decompress).
 517  * Subsequent calls come from consume_markers, below.
 518  */
 519
 520 METHODDEF(void)
 521 start_input_pass (j_decompress_ptr cinfo)
 522 {
 523   per_scan_setup(cinfo);
 524   latch_quant_tables(cinfo);
 525   (*cinfo->entropy->start_pass) (cinfo);
 526   (*cinfo->coef->start_input_pass) (cinfo);
 527   cinfo->inputctl->consume_input = cinfo->coef->consume_data;
 528 }
 529
 530
 531 /*
 532  * Finish up after inputting a compressed-data scan.
 533  * This is called by the coefficient controller after it's read all
 534  * the expected data of the scan.
 535  */
 536
 537 METHODDEF(void)
 538 finish_input_pass (j_decompress_ptr cinfo)
 539 {
 540   (*cinfo->entropy->finish_pass) (cinfo);
 541   cinfo->inputctl->consume_input = consume_markers;
 542 }
 543
 544
 545 /*
 546  * Read JPEG markers before, between, or after compressed-data scans.
 547  * Change state as necessary when a new scan is reached.
 548  * Return value is JPEG_SUSPENDED, JPEG_REACHED_SOS, or JPEG_REACHED_EOI.
 549  *
 550  * The consume_input method pointer points either here or to the
 551  * coefficient controller's consume_data routine, depending on whether
 552  * we are reading a compressed data segment or inter-segment markers.
 553  *
 554  * Note: This function should NOT return a pseudo SOS marker (with zero
 555  * component number) to the caller.  A pseudo marker received by
 556  * read_markers is processed and then skipped for other markers.
 557  */
 558
 559 METHODDEF(int)
 560 consume_markers (j_decompress_ptr cinfo)
 561 {
 562   my_inputctl_ptr inputctl = (my_inputctl_ptr) cinfo->inputctl;
 563   int val;
 564
 565   if (inputctl->pub.eoi_reached) /* After hitting EOI, read no further */
 566     return JPEG_REACHED_EOI;
 567
 568   for (;;) {                    /* Loop to pass pseudo SOS marker */
 569     val = (*cinfo->marker->read_markers) (cinfo);
 570
 571     switch (val) {
 572     case JPEG_REACHED_SOS:      /* Found SOS */
 573       if (inputctl->inheaders) { /* 1st SOS */
 574         if (inputctl->inheaders == 1)
 575           initial_setup(cinfo);
 576         if (cinfo->comps_in_scan == 0) { /* pseudo SOS marker */
 577           inputctl->inheaders = 2;
 578           break;
 579         }
 580         inputctl->inheaders = 0;
 581         /* Note: start_input_pass must be called by jdmaster.c
 582          * before any more input can be consumed.  jdapimin.c is
 583          * responsible for enforcing this sequencing.
 584          */
 585       } else {                  /* 2nd or later SOS marker */
 586         if (! inputctl->pub.has_multiple_scans)
 587           ERREXIT(cinfo, JERR_EOI_EXPECTED); /* Oops, I wasn't expecting this! */
 588         if (cinfo->comps_in_scan == 0) /* unexpected pseudo SOS marker */
 589           break;
 590         start_input_pass(cinfo);
 591       }
 592       return val;
 593     case JPEG_REACHED_EOI:      /* Found EOI */
 594       inputctl->pub.eoi_reached = TRUE;
 595       if (inputctl->inheaders) { /* Tables-only datastream, apparently */
 596         if (cinfo->marker->saw_SOF)
 597           ERREXIT(cinfo, JERR_SOF_NO_SOS);
 598       } else {
 599         /* Prevent infinite loop in coef ctlr's decompress_data routine
 600          * if user set output_scan_number larger than number of scans.
 601          */
 602         if (cinfo->output_scan_number > cinfo->input_scan_number)
 603           cinfo->output_scan_number = cinfo->input_scan_number;
 604       }
 605       return val;
 606     case JPEG_SUSPENDED:
 607       return val;
 608     default:
 609       return val;
 610     }
 611   }
 612 }
 613
 614
 615 /*
 616  * Reset state to begin a fresh datastream.
 617  */
 618
 619 METHODDEF(void)
 620 reset_input_controller (j_decompress_ptr cinfo)
 621 {
 622   my_inputctl_ptr inputctl = (my_inputctl_ptr) cinfo->inputctl;
 623
 624   inputctl->pub.consume_input = consume_markers;
 625   inputctl->pub.has_multiple_scans = FALSE; /* "unknown" would be better */
 626   inputctl->pub.eoi_reached = FALSE;
 627   inputctl->inheaders = 1;
 628   /* Reset other modules */
 629   (*cinfo->err->reset_error_mgr) ((j_common_ptr) cinfo);
 630   (*cinfo->marker->reset_marker_reader) (cinfo);
 631   /* Reset progression state -- would be cleaner if entropy decoder did this */
 632   cinfo->coef_bits = NULL;
 633 }
 634
 635
 636 /*
 637  * Initialize the input controller module.
 638  * This is called only once, when the decompression object is created.
 639  */
 640
 641 GLOBAL(void)
 642 jinit_input_controller (j_decompress_ptr cinfo)
 643 {
 644   my_inputctl_ptr inputctl;
 645
 646   /* Create subobject in permanent pool */
 647   inputctl = (my_inputctl_ptr)
 648     (*cinfo->mem->alloc_small) ((j_common_ptr) cinfo, JPOOL_PERMANENT,
 649                                 SIZEOF(my_input_controller));
 650   cinfo->inputctl = &inputctl->pub;
 651   /* Initialize method pointers */
 652   inputctl->pub.consume_input = consume_markers;
 653   inputctl->pub.reset_input_controller = reset_input_controller;
 654   inputctl->pub.start_input_pass = start_input_pass;
 655   inputctl->pub.finish_input_pass = finish_input_pass;
 656   /* Initialize state: can't use reset_input_controller since we don't
 657    * want to try to reset other modules yet.
 658    */
 659   inputctl->pub.has_multiple_scans = FALSE; /* "unknown" would be better */
 660   inputctl->pub.eoi_reached = FALSE;
 661   inputctl->inheaders = 1;
 662 }